But how do you host services through CGNAT though?
Your issue might be rather that Gmail actually enforces all their guidelines on IPv6 instead of silently degrading your reputation behind the scenes like they do for IPv4. So proper RDNS, SPF and DKIM are tablestakes with DMARC and MTA-STS strongly recommended.
There are some trick for hosting through CGNAT, if you have a server on the outside.
Then it's not internet. Internet means there is no distinction between "servers" and "clients", everyone is a peer.
If you can't host things, you don't have internet. You've just got a modern version of MSN/BTX/Telex/whatever
billions of ppl access the internet thru nat everyday, i'm glad it exists and also happy for alternatives
A caveat is that a lot of people are knowing or unknowingly relying on things like UPnP and NAT-PMP to have services operating normally under NAT. That conveniently masked a lot of the issues with NAT in P2P usecases such as online gaming and torrenting.
Unfortunately, even that is broken under CGNAT.
The more layers of NAT you put on your connection, the more things you break.
though i do defend v4-nat internet as the way it was meant to be, being jailed behind a cgnat w/o repercussions would push me to another isp.
Neither solution works for me though, as someone whose IPv4 connnectivity is behind a CGNAT.
ALL ISPs in my country have deployed CGNAT so there's no "changing ISP" for me either. IPv6 is the only solution left unless I want to pay a premium to get one of those public IPv4 addresses. Really, single-layered IPv4 NAT can't last forever. The address space of IPv4 is simply too limited.
the upnp cargo cult in gaming is real though, despite the prevalence of cgnat.
i agree that you should have choice but am not yet ready to accept that ~11B ppl cannot manage with ~3B addresses given the typical ratio of users per v4 with nat.
Both sides of the internet (provider and user) need an IP address. An average human may possibly require two or more addresses simultaneously (phone, laptop, office PC, and maybe IoT) in the future. And internet infrastructures like routers and managed switches, although never visible to the end users, need an IP address for themselves too. And don't get me started on containerization.
Furthermore, there are internal networks running out of RFC1918 addresses to use so even internal IPv4 has a real limit. Comcast is one of them, T-mobile is another. I believe Facebook moved to IPv6-core because of this too.
People constantly find new ways to use more IP addresses. 4.3B is just too small, even with NAT.
The fact that we are deploying CGNAT everywhere should have made that obvious enough.